Anatomic compatibility of femoral intramedullary implants: a cadaveric study

Abstract

Objective: The purpose of this study was to describe the morphology of the proximal and diaphysis of femur, distribution of neck version, neck-shaft angles, and radius of anterior curvature in a Turkish population to compare with that of femoral intramedullary implants.
Methods: Using 84 cadaveric femora, three-dimensional (3D) modeling was performed with a light scanner, data were transferred to Solidworks 2013 software (Solidworks, Waltham, MA, USA) to determine the variability in the femoral length (FL), neck version, neck-shaft angle (NSA), and anterior bow. Three independent observers’ measurements were tested with a reliability analysis and then evaluated using Cronbach’s alpha value, after which they were compared with the neck-shaft angles, and the radii of curvature (RAC) of intramedullary femoral nails, as stated on the official manufacturer websites.
Results: Mean FL, femoral neck anteversion (FNA), and NSA had ranges of 346.1–454.1 mm, -11.3–40.4°, and 105.9–149.0°, respectively, and RAC was between 1.0 and 1.2 m. The correlation coefficient and 95% confidence intervals (CI) were 0.89 (CI 0.849–0.928), 0.86 (CI 0.799–0.904), and 0.85 (95% CI 0.785–0.898) for FL, FNA, and NSA, respectively. FNA was <10° in 32 femora (37.6%) and >14° 38 (44.7%). NSA was between 130° and 135° in 40 femora (47.1%), and RAC ranged from 0.5 to 1.5 m in 76 femora (91.6%), <1 m in 38 (45.8%), and >1.5 m in 7 (8.4%).
Conclusion: FNA and NSA show a wide distribution, mostly out of the range of intramedullary implants. There is a need for implants that are compatible with a range of NSAs and versions, so that they are suitable for use with a variety of morphologies.

Keywords

• Anatomy; femur; intramedullary nail; light scanner.